RADIO WORKS'™ Dayton Hamvention™, 2009 Brochure

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This version of the CAROLINA WINDOM provides all of the best features of the standard CAROLINA WINDOM, but with an overall length of one-half of the standard CAROLINA WINDOM's length. Performance is nearly identical. The power rating is the same. Only, the length and physical layout are different.

History:

I have been working on making a shorter version of the CAROLINA WINDOM for years. The main limitation was that I didn't want to give up any of the incredible performance the CAROLINA WINDOM offers. The CAROLINA WINDOM Special series was the first reasonable attempt. It was compromised only the lowest frequency band while providing the same performance on all other bands. It is a very popular antenna and provided a way for a lot of folks to have an effective signal in spaces that would normally limit high performance antenna systems.

Various techniques were attempted. Even though I am not a fan of trap antennas, even this technique was tried. Loading coils were also tried and did a better job than traps since it allowed the use of the entire wire length on all bands. Linear loading proved to be very promising, but most common methods adversely affected the multiband qualities of the CAROLINA WINDOM.

Performance was also compromised. I was able to achieve significant shortening, by 50% or even more, with some linear loading geometries and bending techniques. You will probably see some of these in future projects. Unfortunately, production of the best linear loading techniques does not lend themselves to production as they are very labor intensive to build.

One day I just stumbled across a simple buy elegant length reducing technique that worked well with the CAROLINA WINDOM. I had been bending up the active elements in various ways and making lots of measurements and recording the data for later optimization. I was a bit tired of the entire project and an idea I had drawn up several years ago was not yet configured for testing as a shortened CAROLINA WINDOM. I wasn't expecting much, but it was a simple configuration, so I gave it a try. The technique is one that I have recommended against in the usual installation of an antenna. This technique involves bending the antenna back on itself and is one of my cardinals, absolutely no-no, rules.

To make a long story short, I followed the idea I had sketched in my notebook years ago, and I gave it a try. The initial test was a success. The CAROLINA WINDOM continued to function correctly, provided multiband coverage, and presented a decent SWR curve on most bands. It was getting dark, so I attached one of my station's feed lines so that I could listen to band activity. This is often a good test of performance when you have other antennas in the air you can use for comparison. I keep a SuperLoop 80 in the air as well as a G5RV. I have had verticals up, but they are usually not close to the performance of the antennas I'm testing, so I rely on these two antennas or common dipoles. Of course dipoles are the best choice for testing since they are used as standards. However, putting six or eight of them in the air at the same height above ground and with the proper orientation is a difficult proposition. Thus, I rely on antennas that I a very familiar with. The super loop 80 is a very high performance antenna and gives me something to shoot for. The G5RV is one of the most popular antennas, so it's a good choice for a performance bottom line. Any new antenna I make must be better than the G5RV and approach the SuperLoop as closely as possible. I could have used a CAROLINA WINDOM in place of the SuperLoop, but when I'm not testing experimental antennas, a CAROLINA WINDOM occupies the supports used by the test antenna.

Anyway, back to my story; when I got into my radio room later that evening, I listened around the bands, comparing the three antennas. As expected, in most directions, it was the usual order of performance. The G5RV was at the bottom, the test antenna was in the middle and the SuperLoop was at the top. There was a little activity on 20 meters, 40 was OK and 75 was full of the usual signals. The DX window was uninteresting. 20 meters produced some interesting results. In some directions, the new version of the CAROLINA WINDOM was nearly as good as the SuperLoop in most directions and in some directions, it was the SuperLoop's equal or better. This was most unusual because the SuperLoop is supported much higher in the air the test antenna. I use 50 feet for all test antennas. The SuperLoop is almost 100 feet above ground. This performance equivalence definitely captured my attention. What I was observing was a CAROLINA WINDOM that was folded in half but performing just like a standard CAROLINA WINDOM with respect the SuperLoop. The G5RV was down quite a bit in these tests. After further configurations on 20 meters, I turned my attention to 40 meters. Comparing the two antennas on 40 meters produced the same results as on 20. Performance was just what I would have expected from a full size CAROLINA WINDOM. Then, it was back to 75 meters. It was late enough for something to show up in the DX portion of the band and sure enough there was a small pileup. Never one to pass up a pile up, I listened for the fellow's call and gave him a call. I didn't have a linear amplifier hooked up and I was running 100 watts. So, I didn't expect much. Moving off frequency to let the automatic tuner do its thing, I immediately moved back on frequency and gave the DX a call. When he signed with the station, he was working. Like I said, there was a small pileup and I was running barefoot, so I didn't expect much. He came back immediately and give me a good report. Since, as you know, most reports are 5 and 9 no matter what signal report you really deserve, I asked for a critical report, telling him that I was running 100 watts into a RADIO WORKS' SuperLoop 80. The report came back as 5-9 plus 10 which is a nice barefoot report under the prevailing conditions. So, I logged the station and marked the antenna used as the SuperLoop. I always listen on the SuperLoop and then switch to the test antenna for comparison. Was I surprised when I looked at the remote antenna switch and realized that I was using the experimental, folded CAROLINA WINDOM, the CAROLINA WINDOM 80 Compact. What a nice surprise that was. I usually don't apply power until much later in the testing process. That happens after I tweak things a lot and optimize the SWR curves. Power testing is a very careful test procedure. But, then, running 100 watts isn't a challenge in the power department and the SWR was in the range of an automatic tuner, so all was well - especially since the first contact with the antenna was the result of breaking a pileup on 75 meters.

Following such a positive experience, I decided to model the antenna on the computer to see how the computer predicted the comparison between the experimental CAROLINA WINDOM and the standard version. The difference was about 2 dB which is perfectly acceptable for an antenna that is only one-half the length of the standard CAROLINA WINDOM antenna. Moving on to computer models for 7 and 14 MHz produced some interesting results. 40 meter performance was about the same as with a standard CAROLINA WINDOM. 20 meters brought a couple of surprises. In some specific directions and takeoff angles, the experiential version of the CAROLINA WINDOM actually produced a small advantage (3 dB) or so over the standard version. Playing with the geometry of the model produced better results and improved SWR curves. I always take computer modeled results of CAROLINA WINDOMS and similar antennas with a grain-of-salt. That's because it's very difficult to model a CAROLINA WINDOM. There are just too many variables involved. The major problem with the models is the effect of the matching unit which acts as a serries inductance with the Vertical Radiator. The Line Isolator is another complication with the computer models. Still, it did show that there were dimensions and geometries that would produce better results, so that encouraged me to really take a critical look at this new CAROLINA WINDOM variation. Literally, a notebook full of data and weeks of experimentation resulted in the CAROLINA WINDOM Compact as it is currently made. There will definitely be a permanent CAROLINA WINDOM 160 Compact at my QTH.

Following such a positive experience, I decided to model the antenna on the computer to see how the computer predicted the comparison between the experimental CAROLINA WINDOM and the standard version. The difference was about 2 dB which is perfectly acceptable for an antenna that is only one-half the length of the standard CAROLINA WINDOM antenna. Moving on to computer models for 7 and 14 MHz produced some interesting results. 40 meter performance was about the same as with a standard CAROLINA WINDOM. 20 meters brought a couple of surprises. In some specific directions and takeoff angles, the experiential version of the CAROLINA WINDOM actually produced a small advantage (3 dB) or so over the standard version. Playing with the geometry of the model produced better results and improved SWR curves. I always take computer modeled results of CAROLINA WINDOMS and similar antennas with a grain-of-salt. That's because it's very difficult to model a CAROLINA WINDOM. There are just too many variables involved. The major problem with the models is the effect of the matching unit which acts as a serries inductance with the Vertical Radiator. The Line Isolator is another complication with the computer models. Still, it did show that there were dimensions and geometries that would produce better results, so that encouraged me to really take a critical look at this new CAROLINA WINDOM variation. Literally, a notebook full of data and weeks of experimentation resulted in the CAROLINA WINDOM Compact as it is currently made. There will definitely be a permanent CAROLINA WINDOM 160 Compact at my QTH.

Following such a positive experience, I decided to model the antenna on the computer to see how the computer predicted the comparison between the experimental CAROLINA WINDOM and the standard version. The difference was about 2 dB which is perfectly acceptable for an antenna that is only one-half the length of the standard CAROLINA WINDOM antenna. Moving on to computer models for 7 and 14 MHz produced some interesting results. 40 meter performance was about the same as with a standard CAROLINA WINDOM. 20 meters brought a couple of surprises. In some specific directions and takeoff angles, the experiential version of the CAROLINA WINDOM actually produced a small advantage (3 dB) or so over the standard version. Playing with the geometry of the model produced better results and improved SWR curves. I always take computer modeled results of CAROLINA WINDOMS and similar antennas with a grain-of-salt. That's because it's very difficult to model a CAROLINA WINDOM. There are just too many variables involved. The major problem with the models is the effect of the matching unit which acts as a serries inductance with the Vertical Radiator. The Line Isolator is another complication with the computer models. Still, it did show that there were dimensions and geometries that would produce better results, so that encouraged me to really take a critical look at this new CAROLINA WINDOM variation. Literally, a notebook full of data and weeks of experimentation resulted in the CAROLINA WINDOM Compact as it is currently made. There will definitely be a permanent CAROLINA WINDOM 160 Compact at my QTH.

It looks like we have another winner. After optimizing the distance between the main and folded elements and optimizing the droop angles, depth, and offsets, maximum performance was achieved. To further enhance the performance of the CAROLINA WINDOM Compact, the matching unit, Line Isolator and length of the Vertical Radiator had to be optimized. As is usual with the CAROLINA WINDOM, for best matching and maximum radiation at low takeoff angles, each model of the antenna required special modifications of the matching unit and Line Isolator. All the design effort was rewarded with performance from a half-size antenna that is amazingly similar to the full size version. In some cases, since the patterns of the CAROLINA WINDOM and CAROLINA WINDOM Compact are somewhat different, the "Compact" version actually outperforms the standard CAROLINA WINDOM at some directions and specific takeoff angles. In general, the radiation pattern of the standard CAROLINA WINDOM is nearly ideal and this configuration is recommended. That said, there is nothing wrong with the radiation pattern of the CAROLINA WINDOM Compact. The takeoff angle is still very low, but the CAROLINA WINDOM Compact's radiation pattern is not as omnidirectinal as the standard CAROLINA WINDOM. It's about the only compromise the CAROLINA WINDOM Compact makes. Since the difference is only marginal under actual operation conditions where radiation patterns are affected by just about anything metallic in your vicinity, I doubt if you will ever notice the difference. You'll just notice that you are working just about everything you hear and as with all CAROLINA WINDOMS, you hear and work just about any station that anyone else is working, even when they have expensive beams in the air. Of course, I'm not saying that the CAROLINA WINDOM Compact is a "beam beater," but it is very competitive. If you can afford and want to spend the several thousand dollars and put in the weeks of hard work to put a Yagi on a tower, by all means do so. You'll still need the CAROLINA WINDOM or CAROLINA WINDOM Compact for the lower bands. On the other hand, if you want an unequaled general purpose antenna or make a DX "big signal," then you need to look no further than the CAROLINA WINDOM or the CAROLINA WINDOM Compact. Of course, you should start planning where you're going to store all those new QSL cards from around the world.